P0142: O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)
The ECU detects an electrical fault in the heater circuit of the downstream oxygen sensor on bank 1. The heater current is out of range, suggesting an open or shorted heater element, blown fuse or wiring fault.
What P0142 means
P0142 is a generic OBD-II powertrain code in the O2 sensors group. In plain English: the computer found an electrical fault in that circuit: an open, short or bad connection, or a failed component. Bank 1 is the side of the engine with cylinder 1 (inline engines only have bank 1).
- Check engine light
- Usually on
- Emissions-related
- Yes — can fail inspection
- Limp mode possible
- Not typical
- Drive cycle to clear
- Required
Get it fixed
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Symptoms
- Check engine light on after several drive cycles
- Slightly increased fuel consumption during cold start
- Delayed entry into closed-loop fuel control
- Failed emissions inspection (lambda readiness)
Common causes
- 01Sensor heater element openMost likely
- 02Heater fuse blownPossible
- 03Heater wiring or connector faultPossible
Can I drive with P0142?
Usually yes, for a short time.
The car will often drive normally, but get it diagnosed soon. Left alone it can raise fuel use and emissions and will fail an OBD inspection. If you notice rough running, warning lights flashing, overheating or a burning smell, stop driving.
Why we rate it moderate
- Turns on the check engine light
- Emissions-related: will usually fail an OBD inspection
- Needs a drive cycle to confirm a repair
Severity is our rule-based rating from the code’s flags in OBDex and the system it affects, not an inspection of your car. If the check engine light is flashing, or you notice overheating, low oil pressure, or brake or steering problems, stop driving and get help.
How to diagnose P0142
- 1
Confirm the code and save freeze-frame data
Read the codes with an OBD-II scan tool and note every code, not just P0142. Save the freeze-frame data (speed, load, temperature when the fault set) before clearing anything; it tells you when the fault happens.
- 2
Check for related codes first
Look for P0147, P0162, P0167. Related codes often share a cause; a circuit or sensor code usually needs fixing before a performance code like this one.
- 3
Test the circuit
Inspect the wiring and connector at the oxygen sensor (bank 1, sensor 2) and oxygen sensor heater fuse for damage, corrosion or chafing. With a multimeter, check supply voltage, ground and signal against the specifications in the service manual for your vehicle.
- 4
Test the likely causes in order
Start with the most likely cause and work down: Sensor heater element open; heater fuse blown; heater wiring or connector fault. Test before replacing parts.
- 5
Check for recalls and service bulletins
Look up recalls for your exact vehicle with its VIN, and ask a dealer about technical service bulletins (TSBs). Manufacturers sometimes issue software updates or extended warranties for known faults.
- 6
Clear the code and verify the repair
After the repair, clear the code and complete a full drive cycle (cold start, idle, steady highway cruise, deceleration). The code is fixed when the related readiness monitor completes without it returning.
P0142 repair cost estimate
Estimate, not a quote. Labor times are typical ranges for this code from OBDex, and $125/hr is an assumed rate. Shop rates and labor times vary by vehicle and region. Diagnosis time may be billed separately.
- DIY difficulty
- Easy
- Good DIY job?
- Yes, with a scan tool
Basic hand tools; a common first DIY job.
Parts and systems involved
- Oxygen sensor (Bank 1, sensor 2)
- Oxygen sensor heater fuse
- Oxygen sensor heater wiring
P0142 FAQ
What does P0142 mean?
P0142 means “O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)”. The ECU detects an electrical fault in the heater circuit of the downstream oxygen sensor on bank 1. The heater current is out of range, suggesting an open or shorted heater element, blown fuse or wiring fault.
Is P0142 serious? Can I keep driving?
We rate P0142 as moderate severity. Usually yes, for a short time. The car will often drive normally, but get it diagnosed soon. Left alone it can raise fuel use and emissions and will fail an OBD inspection. If you notice rough running, warning lights flashing, overheating or a burning smell, stop driving.
What causes P0142?
The most common causes, from most to least likely: Sensor heater element open; Heater fuse blown; Heater wiring or connector fault. Test before replacing parts, because several causes can set the same code.
How much does it cost to fix P0142?
Typical labor is about $40–$190 at an assumed $125/hour shop rate, plus parts. That is an estimate, not a quote: labor times and rates vary by vehicle and region, and diagnosis may be billed separately.
Can I fix P0142 myself?
DIY difficulty is easy. Many owners can handle it with a scan tool, a multimeter and basic hand tools. Always confirm the cause before buying parts.
Will P0142 clear itself?
Once the fault is fixed, the check engine light usually goes off by itself after the system passes its self-test over several drive cycles. Clearing the code with a scan tool resets readiness monitors, so an inspection station may turn you away until a full drive cycle is completed.